Amplitude and differential cross sections for two-body scattering are calculated using a second-order Feynman diagram of a toy theory (no spin, no charge, no polarization, no color) in the center of mass system. The graphs show the Feynman amplitude ℳ and the differential cross section dσ/dΩ as functions of the scattering angle θ, in radians. You can vary the mass of the exchanged virtual particle and see how the curves behave.